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Re: [Qemu-block] [Qemu-devel] [PATCH] hw/ide/ahci.c: Fix shift left into
From: |
John Snow |
Subject: |
Re: [Qemu-block] [Qemu-devel] [PATCH] hw/ide/ahci.c: Fix shift left into sign bit |
Date: |
Fri, 16 Oct 2015 16:43:24 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 10/16/2015 01:48 PM, Peter Maydell wrote:
> Avoid undefined behaviour from shifting left into the sign bit:
>
> hw/ide/ahci.c:551:36: runtime error: left shift of 255 by 24 places cannot be
> represented in type 'int'
>
> (Unfortunately C's promotion rules mean that in the expression
> "some_uint8_t_variable << 24" the LHS gets promoted to signed
> int before shifting.)
>
> Signed-off-by: Peter Maydell <address@hidden>
> ---
> clang's undefined sanitizer produces a lot of copies of this warning during
> 'make check'...
>
> hw/ide/ahci.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
> index 796be15..21f76ed 100644
> --- a/hw/ide/ahci.c
> +++ b/hw/ide/ahci.c
> @@ -548,7 +548,7 @@ static void ahci_init_d2h(AHCIDevice *ad)
> ad->init_d2h_sent = true;
> /* We're emulating receiving the first Reg H2D Fis from the device;
> * Update the SIG register, but otherwise proceed as normal. */
> - pr->sig = (ide_state->hcyl << 24) |
> + pr->sig = ((uint32_t)ide_state->hcyl << 24) |
> (ide_state->lcyl << 16) |
> (ide_state->sector << 8) |
> (ide_state->nsector & 0xFF);
>
Reviewed-by: John Snow <address@hidden>
Since the "patches" tool seems to still be hiccuping, do you want to
just apply this directly?
--js